The invention relates to inkjet printing apparatus, and particularly to communication between an inkjet print head and a print controller.
An inkjet printing apparatus such as inkjet printer, all-in-one device, multifunction device, typically uses a print controller or a printer host to control and to communicate with an inkjet print head. A thermal inkjet print head generally has a heater chip. The heater chip typically includes logic circuitry, a plurality of power transistors, and a set of heaters or resistors. A hardware or software printer driver will selectively address or energize the logic circuitry such that appropriate resistors are heated for printing. In some heater chip designs, the heater chip includes memory used to store information about the print head. Data stored in the memory is used to identify the print head to determine if the print head is a monochrome print head, a color print head or a photograph quality print head. Data stored in the memory is used to keep track of ink usage.
To communicate data from the print head to the printer, the printer issues a command to the print head. The print head then responds by sending data via electronic digital communication to the printer in order to complete the command. For example, the printer may store ink usage information in memory to read upon print head power up. Upon print head power up, the printer issues a memory read command of the print head ink usage memory. The print head receives and decodes the command, reads the print head memory and responds to the printer with the data. Errors may occur during the electronic digital communication between the print head and printer. For example, a print head may lose mechanical and thus electrical contact during a memory read operation of ink usage. The loss of mechanical contact corrupts the print head memory read operation. The printer may thus interpret the corrupt data as an incorrect level of ink usage, prompting an incorrect indication to the user of the ink level that causes the user to think that the print head has failed to meet the print head's page yield specification.